Which grape variety is extensively cultivated in Oregon, New Zealand's Central Otago, and the Russian River Valley?

The grape variety extensively cultivated in Oregon, New Zealand's Central Otago, and the Russian River Valley is Pinot Noir. This grape is particularly well-suited to cooler climates, which is why it thrives in these regions.

In Oregon, the Willamette Valley has gained a reputation for producing high-quality Pinot Noir, characterized by its elegance and complexity. Similarly, Central Otago in New Zealand has emerged as a premier region for Pinot Noir, showcasing the grape's ability to express the unique terroir of the area with intense fruit flavors and vibrant acidity. The Russian River Valley, located in Sonoma County, California, is also renowned for its exceptional Pinot Noir, benefiting from the region's moderate climate and diverse soil types, which contribute to the complexity and depth of the wines.

While other grape varieties like Cabernet Sauvignon, Merlot, and Syrah are cultivated in various regions, they do not share the same level of prominence specifically in these noted areas. Pinot Noir holds a distinctive place in the viticulture of Oregon, Central Otago, and the Russian River Valley, making it the correct answer for this question.